Refrigerant Compressor

ABSTRACT

The invention provides a refrigerant compressor that is capable of preventing seizure or galling at the bearing slide section and has high anti-wear properties. 
     The refrigerant compressor includes a compressor mechanism for compressing a refrigerant. The compressor mechanism includes a fixed scroll  100  and an orbiting scroll  200 , and the two scrolls are mutually meshed. The refrigerant compressor also includes a rotary shaft  300  for driving the compressor mechanism. A plain bearing(s) is/are provided either at the joint section between the rotary shaft and the compressor mechanism or at the support section supporting the rotary shaft or at both of the two sections. The plain bearing(s) is/are formed of lead-free resin-impregnated material capable of adsorbing wear particles, and the rotary shaft is formed of iron material. The section of the rotary shaft that slides against the plain bearing(s) is covered with a hard film  1000  of a hardness of 1000 Hv or more.

TECHNICAL FIELD

The present invention relates to refrigerant compressors used for cooling or air conditioning purposes and particularly to an improvement in the bearing section of a refrigerant compressor.

BACKGROUND ART

In refrigerant compressors, to prevent seizure of wear of bearings which are sliding parts where mechanical parts slide against each other, surface material adjusted bearing materials are now being developed. For example, to obey the RoHS directive (the directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment), lead-free sliding materials formed mainly of PTFE are used as bearing material so that good sliding properties can be obtained.

As the prior-art technique for the lead-free sliding material formed mainly of PTFE, the one disclosed in Patent Document 1 can be given.

RELATED ART DOCUMENTS Patent Documents

-   Patent Document 1: JP-2002-53673-A

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

The recent trend toward reduced energy consumption has led to demands for efficiency improvement in various industries. Especially, in air conditioners close to dwelling environment, due to the high degree of attention of public opinion, the development of products capable of achieving low costs and high efficiency is demanded.

In air conditioners, after the revision of the energy saving law in 2006, annual performance factors (APF) are used as references indicating efficiency. The APF of an air conditioner is the efficiency of the air conditioner based on use status, and importance is placed on the efficiency at a load region lower than the rated point. For this reason, refrigerant compressors are now frequently operated at low speed.

When a refrigerant compressor is operated at low speed, a sufficient oil film thickness cannot be ensured at the bearing (sliding component), and the oil tends to be in the boundarylubricationregion. Further, since the refrigerant dissolves into the refrigerating oil, oil viscosity decreases. As a result, metal contact may occur, and seizure, galling or wear is more likely to occur, resulting in reduced performance or quality of the refrigerant compressor.

An object of the invention is to obtain a refrigerant compressor that is capable of preventing seizure or galling at the bearing slide section and has high anti-wear properties.

Means for Solving the Problems

To solve the above problems, the present invention provides a refrigerant compressor comprising: a compressor mechanism for compressing a refrigerant; a rotary shaft for driving the compressor mechanism; a plain bearing located either at a joint section between the rotary shaft and the compressor mechanism or at a support section supporting the rotary shaft or plain bearings located at both of the joint section and the support section, wherein the plain bearing(s) is/are formed of a lead-free resin-impregnated material capable of adsorbing wear particles, wherein the rotary shaft is formed of an iron material, and wherein a section of the rotary shaft that comes into contact with the plain bearing(s) is covered with a hard film of a hardness of 1,000 Hv or more.

Effect of the Invention

The present invention has the effect of obtaining a refrigerant compressor that is capable of preventing seizure or galling at the bearing slide section and has high anti-wear properties.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross section showing Embodiment 1 of the refrigerant compressor of the invention;

FIG. 2 is an enlarged cross section near the plain bearings of FIG. 1;

FIG. 3 is a graph showing the relationship between the hardness of a hard film covering the rotary shaft and the bearing wear rate;

FIG. 4 is a diagram illustrating a modification of FIG. 2 and an enlarged cross section corresponding to FIG. 2;

FIG. 5 is an enlarged cross section explaining an example in which a hard film is provided on a base material;

FIG. 6 is an enlarged cross section explaining another example in which a hard film is provided on a base material; and

FIG. 7 is an enlarged cross section explaining a still another example in which a hard film is provided on a base material.

MODE FOR CARRYING OUT THE INVENTION

The annual performance factor (APF) in an air conditioner is the efficiency of the air conditioner based on use status, and importance is placed on the efficiency at a load region lower than the rated point. For this reason, refrigerant compressors are often operated at low speed.

However, when a refrigerant compressor is operated at low speed, as stated above, the oil film thickness at the bearing cannot be ensured sufficiently at low speed, and the oil is likely to shift to the boundary lubrication region. As a result, metal contact occurs, and seizure, galling or wear is more likely to occur, resulting in reduced performance or quality of the refrigerant compressor.

As the bearing of a refrigerant compressor, as disclosed in Patent Document 1, resin material such as PTFE which is an impregnated material is also used. Such resin material has foreign substance adsorbing capabilities with which to adsorb wear particles (foreign substances) such as metal particles into the resin material, and thus has the effect of reducing seizure or wear due to wear particles. However, we have found out that under the situation where the oil film thickness of the baring lubricating oil decreases significantly at low speed, metal particles (wear particles) adsorbed into the resin material may come into metal contact with the rotary shaft, resulting in seizure or galling.

A specific embodiment for solving the above problem is explained below based on the drawings.

Embodiment 1

FIG. 1 is a vertical cross section of a refrigerant compressor (scroll compressor) according to Embodiment 1 of the invention.

A sealed vessel 700 houses a compressor mechanism (located above), an electric motor 600 (located in the middle), and an oil sump 730 (located below). The compressor mechanism and the electric motor 600 are connected to each other via a rotary shaft 300 formed of iron material. The compressor mechanism includes two scrolls: a fixed scroll 100 having an end plate 101 and a vertically extending spiral wrap 102 and an orbiting scroll 200 having an end plate 201 and a vertically extending spiral wrap 202. The spiral warp 102 meshes with the spiral warp 202, thereby forming the compressor mechanism. The fixed scroll 100 also includes a gas inlet 103 and a gas outlet 104. The rotary shaft 300 is supported by a plain bearing (primary bearing) 401 and a secondary bearing 801. The plain bearing 401 lies within an upper frame 400 located above the electric motor 600 while the secondary bearing 801 lies within a lower frame 800 located below the electric motor 600. The upper frame 400 and the lower frame 800 are secured to the sealed vessel 700. An eccentric crank pin 301 formed of iron material is disposed at the upper end of the rotary shaft 300 and engages within a boss section 203 located below the end plate 201 of the orbiting scroll 200. Located within the boss section 203 is an orbiting plain bearing 210 within which the crack pin 301 slides. An Oldham coupling 500 is also located at the back side of the end plate 201 of the orbing scroll 200 and allows the orbiting scroll 200 to orbit with respect to the fixed scroll 100 without rotating.

When the electric motor 600 drives the rotary shaft 300 connected to its rotor, the crack pin 301 located at the upper end of the rotary shaft 300 is caused to rotate eccentrically. This in turn causes the orbiting scroll 200 to orbit with respect to the fixed scroll 100. During the orbital movement, the anti-rotating mechanism of the Oldham coupling 500 prevents the orbiting scroll 200 from rotating. The orbital movement of the orbiting scroll 200 is followed by the introduction of gas into one of the successive enclosed spaces formed by spiral wraps 102 and 202 through an inlet pipe 711 and the gas inlet 103. As the orbital movement continues, the enclosed space containing the gas moves toward the scroll center and decreases in volume, thereby compressing the gas. The compressed gas is discharged through the gas outlet 104 to an outlet chamber 710. The gas discharged into the outlet chamber 710 is then transferred around the compressor mechanism and the electric motor 600 and eventually discharged out of the scroll compressor through an outlet pipe 701.

We now describe how lubricating oil circulates. A bearing housing 802, designed to house the secondary bearing 801, is attached to the lower frame 800, and a pump 900 is disposed below the bearing housing 802. The pump 900 is driven via a pump joint 310 attached to the lower end of the rotary shaft 300. When the rotary shaft 300 starts to rotate, the pump 900 suctions oil from the oil sump 730, followed by the transfer of the oil through the oil passageway 311 within the rotary shaft 300 up to the top section of the crack pin 301. The oil then lubricates the orbiting plain bearing 210 and flows along the plain bearing 401. After lubricating the plain bearing 401, the oil passes through an oil pipe 408 to return to the oil sump 730.

It should be noted that part of the oil that has lubricated the orbiting plain bearing 210 passes the seal section 402 located between the bottom surface of the boss section 203 of the orbiting scroll and the upper frame 400, flows to the back surface of the end plate 201 of the orbiting scroll, and from here, through an oil passageway 220 formed in the orbiting scroll end plate 201, lubricates the slide sections between the fixed scroll 100 and the orbiting scroll 200 and lubricates between the wraps 102 and 202, and is discharged into the outlet chamber 710 with the compressed gas. Thereafter, the oil discharged into the outlet chamber 710 returns to the oil sump 730 located at the bottom of the sealed vessel 700.

FIG. 2 is an enlarged cross section of a section near the orbiting plain bearing 210 and the plain bearing (primary bearing) 401 shown in FIG. 1 where the components assigned the same reference numerals as those used in FIG. 1 represent the same components.

In this embodiment, a lead-free resin-impregnated material is used for the plain bearings such as the orbiting plain bearing 210 and the plain bearing 401, and at the same time, a hard film 1000 of a hardness of 1000 Hv or more (preferably 1500 Hv or more) is provided on the surface (outer surface) of the rotary shaft 300 that slides against the plain bearing (primary bearing) 401 and on the surface (outer surface) of the crack pin 301 that slides against the orbiting plain bearing 210.

As the lead-free resin-impregnated material, resin material having foreign substance adsorbing capabilities such as PTFE (polytetrafluoroethylene) is used. As resin material having foreign substance adsorbing capabilities, POM (polyacetal), PBT (polybutylene terephthalate), PPS (polyphenylene sulfide), PEEK (polyether ether ketone), and or the like can also be used. With the use of such resin material having foreign substance adsorbing capabilities, wear particles (foreign substances) such as metal particles can be adsorbed into the resin material. Accordingly, seizure or wear of the plain bearings due to the wear particles can be reduced.

However, when the refrigerant compressor is operated at low speed, oil film shortage may occur under the situation where the oil film thickness of the bearing lubricating oil decreases significantly. In such a case, in a lead-free resin-impregnated bearing with high foreign substance adsorbing capabilities, metal particles (wear particles) adsorbed come into metal contact with the rotary shaft (the crack pin included), resulting in seizure or galling.

Because, for such problems, in this embodiment, the hard film 1000 of a hardness of 1000 Hv or more (preferably 1500 Hv or more) is provided on the surface (outer surface) of the rotary shaft 300 that slides against the plain bearing 401 and on the surface (outer surface) of the crack pin 301 that slides against the orbiting plain bearing 210, wear of the rotary shaft and the crank pin due to the wear particles and the occurrence of seizure or linear scars can be reduced significantly. In other words, because in the refrigerant compressor, almost all the hardnesses of wear particles adsorbed into the lead-free resin-impregnated bearings are less than 1000 Hv, wear of the rotary shaft 300 (the crank pin included) due to the wear particles and the occurrence of seizure or linear scars can be reduced significantly, and it was found out that especially when a hard film of 1500 Hv or more is used, seizure, galling or wear of the rotary shaft hardly progresses.

However, if the hardness of the hard film is further increased, the effect on wear or linear scars of the rotary shaft is almost the same, but if the hardness is increased excessively, for example if a hard film of a hardness far greater than 3000 Hv, for example, of a hardness of 4000 Hv is used, due to the influence of the coarseness or irregularities of the surface of the rotary shaft or due to irregularities of the shaft surface resulting from peeling of the hard film, wear of the lead-free resin-impregnated bearings that slide against it is more likely to progress, which is not desirable.

FIG. 3 is a graph illustrating the relationship between the hardness of the hard film covering the rotary shaft and the bearing wear rates of the lead-free resin-impregnated bearings. This graph was confirmed by subjecting the refrigerant compressor (scroll compressor) to stress tests at the boundary lubrication region in which the oil film is difficult to form at low speed, and the horizontal axis represents the types of slid films covering rotary shafts (hardness of the hard films). Non-coat (A) is a rotary shaft with no hard film whose hardness is about 600 Hv, and to form this rotary shaft, S45C was used as iron material, and its slide section was subjected to quenching treatment. DLC (B) is an iron rotary shaft around which was applied a DLC (diamond-like carbon) film of a hardness of 3000 Hv, and DLC (C) is an iron rotary shaft around which was applied a DLC film of a hardness of 4000 Hv. Also, while the bearing wear rate of a lead-free resin-impregnated bearing having foreign substance adsorbing capabilities that slides against the rotary shaft of non-coat (A) is used as a reference (100), the vertical axis represents the bearing wear rates (comparative wear rates) of lead-free resin-impregnated bearings having foreign substance adsorbing capabilities that slide against the rotary shafts DLC (B) and DLC (C) having other hard films.

From FIG. 3, when the rotary shaft covered with a DLC film of a hardness of 3000 Hv was used, the bearing wear rate of the lead-free resin-impregnated bearing having foreign substance adsorbing capabilities that slide against it decreased more than when the rotary shaft of non-coat (A) was used. Also, the damage status of the rotary shaft and the bearing after sliding was good, and no linear scars were found on the rotary shaft and the bearing.

On the other hand, when the rotary shaft covered with a DLC film of a hardness of 4000 Hv was used, the bearing wear rate increased more than when the rotary shaft of non-coat (A) was used. Also, we confirmed the occurrence of linear scars on the bearing after sliding.

From the results shown in FIG. 3, we have found out that by using a rotary shaft covered with a hard film of a hardness of 3000 Hv or less, the bearing wear rate of the lead-free resin-impregnated bearing having foreign substance adsorbing capabilities can be decreased, and that at the same time, the occurrence of linear scars can be prevented.

Also, to prevent seizure or galling even if the rotary shaft is in contact with wear particles such as metal particles and maintain the shaft in a good condition, as stated above, it is preferred to use a rotary shaft covered with a hard film of a hardness of 1000 Hv or more. Accordingly, in the present embodiment, by applying a hard film of a hardness range of 1000 Hv to 3000 Hv (preferably 1500 to 3000 Hv), the occurrence of seizure or galling in the bearing slide sections such as orbiting plain bearing 210, the plain bearing 401, the rotary shaft 300, the crank pin 301, and the like can be prevented. Since wear can also be prevented, a highly reliable refrigerant compressor capable of improving anti-wear properties can be obtained.

FIG. 4 is one showing a modification of FIG. 2 where the components assigned the same reference numerals as those used in FIG. 2 represent the same or corresponding components. While the example of FIG. 2 is one in which the layer of the hard film 1000 is directly formed by vapor deposition on the outer surface of the rotary shaft (the crank pin included) 300, in the example shown in FIG. 4, a hard film is provided by engaging a cylindrical member 302 formed of iron material covered with the hard film 1000 with the surfaces of the rotary shaft 300 and the crank pin 301 that slide against the orbiting plain bearing 210 and the plain bearing 401. In other words, a hard film of a hardness of 1000 Hv or more (preferably 1500 Hv or more) is formed in advance on the outer surface of the iron cylindrical member 302 by vapor deposition, the cylindrical member 302 is engaged with the locations of the rotary shaft 300 and the crank pin 301 that slide against the orbing plain bearing 210 and the plain bearing 410. According to this example, compared with the example shown in FIG. 2, productivity can be increased about five to ten times, and as a result, the costs of the refrigerant compressor can be reduced.

FIG. 5 is a diagram illustrating the structure of the base materials (the rotary shaft 300 and the cylindrical member 302) and the hard film 1000 shown in FIGS. 2 and 4.

In FIG. 5, the component that acts as the base material on the surface of which a hard film is formed is the rotary shaft (including the crank pin) 300 shown in FIG. 2 or the cylindrical member 302 engaged with the rotary shaft as shown in FIG. 4. On the surfaces of these base materials, the hard film 1000 of a hardness of for example 1500 Hv is formed. As the hard film 1000, a Cr-based film (for example CrN), Ti-based film (for example TiN), DLC film, Si-DLC film or the like can be used. These hard films 1000 can be formed on the base materials by vapor deposition, thereby forming the hard film on the surfaces of the base materials. Also, any of the aforementioned hard films has high corrosion resistance, is high in hardness, shows low friction coefficients, and is suitable as the sliding materials that slide against the plain bearings. Especially, in DLC (diamond-like carbon) which is a diamond-like film, there are SP³ bonds constituting diamond and SP² bonds having the graphite structure, and its hardness can be adjusted by adjusting coating conditions and varying bonding ratios.

Because each of the aforementioned hard films is capable of increasing surface smoothness, physical friction and wear are unlikely to occur, and a hard film of a hardness of 1500 Hv or more can be obtained with ease. Thus, by providing any of the aforementioned hard films on the rotary shaft surface that slides against the plain bearings, the occurrence of seizure or galling at the bearing slide sections can be prevented, and a refrigerant compressor capable of improving anti-wear properties can be obtained.

FIG. 6 is an enlarged cross section explaining another example in which a hard film is provided on the base materials, and the components assigned the same reference numerals as those used in FIG. 5 represent the same components. In the example of FIG. 5, when the hardness of the iron material (base material) constituting the rotary shaft 300 is low, if a hard film of high hardness, for example, a DLC film of high hardness is formed, the hardness difference between the two is large, and while the refrigerant compressor is being operated, peeling of the hard film 1000 may occur due to deformation of the slide section. The example of FIG. 6 is one explaining the method of forming a hard film on the base materials, which is effective in preventing peeling of the hard film 1000.

This example is one in which between the hard film 1000 and the base materials (the rotary shaft 300 and the cylindrical 302), an intermediate layer 1001 having an intermediate hardness between the base materials and the hard film is provided. In other words, using the rotary shaft 300 and the cylindrical member 302 formed of iron material as the base materials, the intermediate layer 1001 formed of a Cr-based film of a hardness of 1000 to 1500 Hv is formed on the base materials, and the hard film 1000 formed of a DLC film of a hardness of 2000 to 3000 Hv is formed on the intermediate layer 1001. According to this example, because a hard film of greater hardness can be formed on the slide surface, wear or galling of the bearing slide section can be prevented, and at the same time, because the Cr-based film having high adhesiveness with respect to the iron material is formed as the intermediate layer 1001, a refrigerant compressor capable of preventing peeling of the hard film and higher in reliability can be obtained. In this example, too, the intermediate layer 1001 and the hard film 1000 can be formed by vapor deposition or the like.

FIG. 7 is an enlarged cross section explaining still another example in which a hard film is provided on the base materials, and the components assigned the same reference numerals as those used in FIG. 5 represent the same components. The example of FIG. 7 is the same as the example of FIG. 5 in that the rotary shaft 300 and the cylindrical member 302 formed of iron material are used as the base materials and the hard film 1000 is formed on the base materials. However, the example of FIG. 7 is distinctive in that the hard film 1000 is a tilted film whose hardness gradually increased from the base material side toward the slide surface side. In this example, an Si-DLC film is used as the hard film 1000, and this film is a tilted film whose Si amount (Si concentration) gradually decreased from the base material surface side toward the slide surface side. The hardness of the hard film 1000 on the base material side is 1000 Hv or thereabout, and the hardness on the slide surface side is 1500 Hv or more. The hard film formed of such a tilted film, too, can be formed on the surfaces of the base materials by vapor deposition.

As the method of not forming a complete boundary between the lower layer (base material side) and the upper layer (slide surface side) in the hard film 1000 and forming a tilted film that gradually changes from DLC to Si-DLC from the slide surface side to the base material side, the ion plating (IP) method, ion vapor deposition, and sputtering method are available. Other methods can also be employed as long as the desired hardness range can be achieved.

Here we describe a method for forming the Si-DLC tilted film using the arc ion plating (AlP) method, a type of the IP method. In the AlP method, the base materials (the rotary shaft 300 and the cylindrical member 302) are placed within a vacuum chamber of a vacuum degree of 10³ to 10⁻⁵ Pa, and negative bias is applied to the materials. Meanwhile ionized materials for forming a hard film are electrically accelerated and caused to collide with the base materials, thereby forming a hard film on the surfaces of the base materials.

When a Si-DLC hard film is formed, for the formation of DLC, hydrocarbon-based gas such gas as C⁶H⁶ or C²H² is introduced, and as the material of Si which is an additive material, silane-based gas such as tetramethylsilane or the like is introduced.

By introducing the hydrocarbon-based gas and the silane-based gas into the vacuum chamber at the time of the start of vapor deposition using the AlP method, a Si-DLC film is first formed on the surfaces of the base materials according to the amount of the silane-based gas introduced. Thereafter, by reducing the amount of the silane-based gas gradually, a tilted film whose Si concentration gradually decreases from the base material side toward the slide surface side can be formed. In the Si-DLC film, the higher the Si concentration, the lower the hardness, and the lower the Si concentration, the higher the hardness. Thus, as to the base material side, the hardness is set to the hardness close to the hardness of the base materials (for example, 1000 Hv), and the hardness can be made greater toward the slide surface side. At the slide surface, the hardness can be set to 2000 to 3000 Hv.

By doing so, high sliding properties can be obtained even in the metal contact at the initial sliding, and at the same time, because the Si amount increased gradually toward the base materials, the adhesiveness between the hard film and the base materials can be increased, and peeling of the hard film is unlikely to occur. Thus, according to this example, there is the effect of obtaining a refrigerant compressor capable of increasing reliability further. The Si amount of the hard film 1000 close to the base materials is preferred about 20 at. % in light of the adhesiveness with respect the base materials.

According to the aforementioned embodiment, the plain bearings are formed by using lead-free resign-impregnated material having foreign substance adsorbing capabilities with which to adsorb wear particles, and the rotary shaft is formed of iron material. Also, a hard film of a hardness of 1000 Hv or more is provided at the section of the rotary shaft that slides against the plain bearings. Thus, even if the oil film thickness at the plain bearings decreases with the refrigerant compressor operated at low speed, a highly reliable refrigerant compressor capable of preventing the occurrence of seizure or galling at the slide surface between the rotary shaft and the lead-free resin-impregnated bearings can be obtained.

In other words, by the use of lead-free resin-impregnated material having foreign substance adsorbing capabilities, wear particles can be adsorbed into the lead-free resin-impregnated material. Thus, the occurrence of seizure or wear at the rotary shaft and the plain bearings can be reduced. At the same time, even if the wear particles adsorbed come into metal contact with the rotary shaft with the oil film thickness not secured at low speed and with the oil shifting to the boundary lubrication region, seizure or galling of the rotary shaft can be prevented, and good sliding capabilities can be ensured because the hard film harder and better in sliding capabilities than wear particles are provided on the rotary shaft surface. Thus, according to the present embodiment, it is possible to obtain a highly reliable refrigerant compressor capable of preventing the occurrence of seizure or galling at the bearing slide section when the refrigerant compressor is being operated at low speed, of obtaining good sliding capabilities, and of improving anti-wear properties.

DESCRIPTION OF THE REFERENCE NUMERALS

-   100: Fixed scroll (101: End plate, 102: Wrap, 103: Gas inlet, 104:     Gas outlet) -   200: Orbiting scroll (201: End plate, 202: Wrap, 203: Boss section,     210: Orbiting plain bearing, 220: Oil passageway) -   300: Rotary shaft (301: Crank pin, 302: Cylindrical member, 310:     Pump joint, 311: Oil passageway) -   400: Upper frame (401: Plain bearing, 402: Seal section, 408: Oil     pipe) -   500: Oldham-coupling Ring -   600: Electric motor -   700: Sealed vessel (701: Discharge pipe, 710: Outlet chamber, 711:     Suction pipe, 730: Oil sump) -   800: Lower frame (801: Secondary bearing, 802: Bearing housing) -   900: Pump -   1000: Hard film -   1001: Intermediate layer 

1. A refrigerant compressor comprising: a compressor mechanism for compressing a refrigerant; a rotary shaft for driving the compressor mechanism; and a plain bearing located either at a joint section between the rotary shaft and the compressor mechanism or at a support section supporting the rotary shaft or plain bearings located at both of the joint section and the support section, wherein the plain bearing(s) is/are formed of a lead-free resin-impregnated material capable of adsorbing wear particles, wherein the rotary shaft is formed of an iron material, and wherein a section of the rotary shaft that comes into contact with the plain bearing(s) is covered with a hard film of a hardness of 1,000 Hv or more.
 2. The refrigerant compressor of claim 1 wherein the hardness of the hard film is in the range of 1,500 to 3,000 Hv.
 3. The refrigerant compressor of claim 1 wherein the hard film covers an outer surface of a cylindrical member formed of iron material, and the cylindrical member is engaged with the rotary shaft.
 4. The refrigerant compressor of claim 1 wherein the hard film is either a Cr-based film, a Ti-based film, a DLC-based film, or an Si-DLC film.
 5. The refrigerant compressor of claim 4 wherein the hard film includes a Cr-based film deposited on a surface of the iron material constituting the rotary shaft and a DLC-based film deposited on the Cr-based film, the DLC-based film being higher in hardness than the Cr-based film.
 6. The refrigerant compressor of claim 4 wherein the hard film is an Si-DLC film and wherein the Si-DLC film is formed into a tiled film whose Si concentration decreases from the surface of the iron material constituting the rotary shaft toward a slide surface.
 7. The refrigerant compressor of claim 1 wherein the compressor mechanism is a scroll compressor comprising a fixed scroll and an orbiting scroll, each having an end plate and a spiral wrap. 